Neuromonitoring in paediatric anaesthesia

Electroencephalographic Indices for Clinical Endpoints during Propofol Anesthesia in Infants: An Early-phase Propofol Biomarker-finding Study

BACKGROUND

Unlike expired sevoflurane concentration, propofol lacks a biomarker for its brain effect site concentration, leading to dosing imprecision particularly in infants. Electroencephalography monitoring can serve as a biomarker for propofol effect site concentration, yet proprietary electroencephalography indices are not validated in infants. The authors evaluated spectral edge frequency (SEF95) as a propofol anesthesia biomarker in infants. It was hypothesized that the SEF95 targets will vary for different clinical stimuli and an inverse relationship existed between SEF95 and propofol plasma concentration.

METHODS

This prospective study enrolled infants (3 to 12 months) to determine the SEF95 ranges for three clinical endpoints of anesthesia (consciousness-pacifier placement, pain-electrical nerve stimulation, and intubation-laryngoscopy) and correlation between SEF95 and propofol plasma concentration at steady state. Dixon's up-down method was used to determine target SEF95 for each clinical endpoint. Centered isotonic regression determined the dose-response function of SEF95 where 50% and 90% of infants (ED50 and ED90) did not respond to the clinical endpoint. Linear mixed-effect model determined the association of propofol plasma concentration and SEF95.

RESULTS

Of 49 enrolled infants, 44 evaluable (90%) showed distinct SEF95 for endpoints: pacifier (ED50, 21.4 Hz; ED90, 19.3 Hz), electrical stimulation (ED50, 12.6 Hz; ED90, 10.4 Hz), and laryngoscopy (ED50, 8.5 Hz; ED90, 5.2 Hz). From propofol 0.5 to 6 μg/ml, a 1-Hz SEF95 increase was linearly correlated to a 0.24 (95% CI, 0.19 to 0.29; P < 0.001) μg/ml decrease in plasma propofol concentration (marginal R2 = 0.55).

CONCLUSIONS

SEF95 can be a biomarker for propofol anesthesia depth in infants, potentially improving dosing accuracy and utilization of propofol anesthesia in this population.

EDITOR’S PERSPECTIVE

Quantitative electroencephalogram in term neonates under different sleep states

Electroencephalogram (EEG) can be used to assess depth of consciousness, but interpreting EEG can be challenging, especially in neonates whose EEG undergo rapid changes during the perinatal course. EEG can be processed into quantitative EEG (QEEG), but limited data exist on the range of QEEG for normal term neonates during wakefulness and sleep, baseline information that would be useful to determine changes during sedation or anesthesia. We aimed to determine the range of QEEG in neonates during awake, active sleep and quiet sleep states, and identified the ones best at discriminating between the three states. Normal neonatal EEG from 37 to 46 weeks were analyzed and classified as awake, quiet sleep, or active sleep. After processing and artifact removal, total power, power ratio, coherence, entropy, and spectral edge frequency (SEF) 50 and 90 were calculated. Descriptive statistics were used to summarize the QEEG in each of the three states. Receiver operating characteristic (ROC) curves were used to assess discriminatory ability of QEEG. 30 neonates were analyzed. QEEG were different between awake vs asleep states, but similar between active vs quiet sleep states. Entropy beta, delta2 power %, coherence delta2, and SEF50 were best at discriminating awake vs active sleep. Entropy beta had the highest AUC-ROC ≥ 0.84. Entropy beta, entropy delta1, theta power %, and SEF50 were best at discriminating awake vs quiet sleep. All had AUC-ROC ≥ 0.78. In active sleep vs quiet sleep, theta power % had highest AUC-ROC > 0.69, lower than the other comparisons. We determined the QEEG range in healthy neonates in different states of consciousness. Entropy beta and SEF50 were best at discriminating between awake and sleep states. QEEG were not as good at discriminating between quiet and active sleep. In the future, QEEG with high discriminatory power can be combined to further improve ability to differentiate between states of consciousness.

A Narrative Review Illustrating the Clinical Utility of Electroencephalogram-Guided Anesthesia Care in Children

The major therapeutic end points of general anesthesia include hypnosis, amnesia, and immobility. There is a complex relationship between general anesthesia, responsiveness, hemodynamic stability, and reaction to noxious stimuli. This complexity is compounded in pediatric anesthesia, where clinicians manage children from a wide range of ages, developmental stages, and body sizes, with their concomitant differences in physiology and pharmacology. This renders anesthetic requirements difficult to predict based solely on a child's age, body weight, and vital signs. Electroencephalogram (EEG) monitoring provides a window into children's brain states and may be useful in guiding clinical anesthesia management. However, many clinicians are unfamiliar with EEG monitoring in children. Young children's EEGs differ substantially from those of older children and adults, and there is a lack of evidence-based guidance on how and when to use the EEG for anesthesia care in children. This narrative review begins by summarizing what is known about EEG monitoring in pediatric anesthesia care. A key knowledge gap in the literature relates to a lack of practical information illustrating the utility of the EEG in clinical management. To address this gap, this narrative review illustrates how the EEG spectrogram can be used to visualize, in real time, brain responses to anesthetic drugs in relation to hemodynamic stability, surgical stimulation, and other interventions such as cardiopulmonary bypass. This review discusses anesthetic management principles in a variety of clinical scenarios, including infants, children with altered conscious levels, children with atypical neurodevelopment, children with hemodynamic instability, children undergoing total intravenous anesthesia, and those undergoing cardiopulmonary bypass. Each scenario is accompanied by practical illustrations of how the EEG can be visualized to help titrate anesthetic dosage to avoid undersedation or oversedation when patients experience hypotension or other physiological challenges, when surgical stimulation increases, and when a child's anesthetic requirements are otherwise less predictable. Overall, this review illustrates how well-established clinical management principles in children can be significantly complemented by the addition of EEG monitoring, thus enabling personalized anesthesia care to enhance patient safety and experience.

Emergence agitation in paediatric day case surgery: A randomised, single-blinded study comparing narcotrend and heart rate variability with standard monitoring

BACKGROUND

Postoperative emergence agitation remains a significant challenge in paediatric anaesthesia. Although short-lived, it may cause harm to the patient and negative experiences for all. Differentiating agitation, delirium and pain is difficult. Electroencephalography allows precise titration of anaesthetic depth, and heart rate variability monitoring permits immediate intervention regarding nociception and pain. We examined if one of these measures could be used to reduce postoperative agitation in an unselected paediatric day surgical population.

OBJECTIVE

The primary outcome was postoperative agitation with a Richmond Agitation-Sedation Scale greater than 0. Secondary outcomes were: length of stay, postoperative nausea and vomiting, fentanyl and propofol consumption, pain scores and use of postoperative analgesics.

DESIGN

A randomised, single-blinded study constituting children aged 1 to 6 years, undergoing minor general day surgical procedures.

SETTING

Paediatric day surgical department 29th March 2019 to 12th June 2020.

PATIENTS

Ninety-eight children (ASA 1 or 2) were enrolled, and 93 children were included in the final analysis.

INTERVENTIONS

Children received standard monitoring (n=31), standard monitoring plus either Narcotrend (n=31), or Anaesthesia Nociception Index monitoring (n=31). Sevoflurane or fentanyl was titrated immediately according to monitor thresholds.

RESULTS

Kaplan-Meier analysis yielded a statistically significant difference between the groups (P = 0.016) with the lowest agitation levels in the Anaesthesia Nociception Index group, intermediate levels in the control group and the highest agitation levels in the Narcotrend monitored group. Intergroup pairwise comparison however, showed no difference. The Anaesthesia Nocioception Index group received slightly more fentanyl (P = 0.277). The control group patients had the highest pain scores despite receiving more caudal blocks and the Narcotrend group had more sevoflurane adjustments. Other secondary outcomes were comparable.

CONCLUSION

Children in the Anaesthesia Nociception Index group were the least agitated with the highest fentanyl doses, without increasing the length of stay in the PACU or postoperative nausea and vomiting.

CLINICAL REGISTRATION

The study was registered in RedCAP online trial database 1/11/2018 trial registration nr. OP720. https://open.rsyd.dk/OpenProjects/openProject.jsp?openNo=720&lang=da.

Using Electroencephalography (EEG) to Guide Propofol and Sevoflurane Dosing in Pediatric Anesthesia

Sevoflurane and propofol-based anesthetics are dosed according to vital signs, movement, and expired sevoflurane concentrations, which do not assess the anesthetic state of the brain and, therefore, risk underdose and overdose. Electroencephalography (EEG) measures cortical brain activity and can assess hypnotic depth, a key component of the anesthetic state. Application of sevoflurane and propofol pharmacology along with EEG parameters can more precisely guide dosing to achieve the desired anesthetic state for an individual pediatric patient. This article reviews the principles underlying EEG use for sevoflurane and propofol dosing in pediatric anesthesia and offers case examples to illustrate their use in individual patients.

Applications and Limitations of Neuro-Monitoring in Paediatric Anaesthesia and Intravenous Anaesthesia: A Narrative Review

Safe management of anaesthesia in children has been one of the top areas of research over the last decade. After the large volume of articles which focused on the putative neurotoxic effect of anaesthetic agents on the developing brain, the attention and research efforts shifted toward prevention and treatment of critical events and the importance of peri-anaesthetic haemodynamic stability to prevent negative neurological outcomes. Safetots.org is an international initiative aiming at raising the attention on the relevance of a high-quality anaesthesia in children undergoing surgical and non-surgical procedures to guarantee a favourable outcome. Children might experience hemodynamic instability for many reasons, and how the range of normality within brain autoregulation is maintained is still unknown. Neuro-monitoring can guide anaesthesia providers in delivering optimal anaesthetic drugs dosages and also correcting underling conditions that can negatively affect the neurological outcome. In particular, it is referred to EEG-based monitoring and monitoring for brain oxygenation.

The risk factors for delayed recovery in patients with cardiopulmonary bypass: Why should we care?

Cardiopulmonary bypass (CPB) is very commonly performed among the cardiovascular surgeries, and delayed recovery (DR) is a kind of serious complications in patients with CPB. It is necessary to assess the risk factors for DR in patients with CPB, to provide evidence into the management of CPB patients.Patients undergoing CPB in our hospital from January 2018 to March 2020 were included. Cases that consciousness has not recovered 12 hours after anesthesia were considered as DR. The preoperative and intraoperative variables of CPB patients were collected and analyzed. Logistic regressions were conducted to analyze the potential influencing factor.A total of 756 CPB patients were included, and the incidence of DR was 9.79%. There were significant differences on the age, aspartate aminotransferase (AST), glutamic pvruvic transaminase (ALT), blood urea nitrogen (BUN), and serum creatinine (SCr) between patients with and without DR (all P < .05); there were no significant differences in the types of surgical procedure (all P > .05); there were significant differences on the duration of CPB, duration of aortic cross clamp (ACC), duration of surgery, minimum nasopharyngeal temperature, and transfusion of packed red blood cells between patients with and without DR (all P < .05). Logistic regression analysis indicated that duration of CPB ≥132 minutes (odds ratio [OR] 4.12, 1.02-8.33), BUN ≥9 mmol/L (OR 4.05, 1.37-8.41), infusion of red blood cell suspension (OR 3.93, 1.25-7.63), duration of surgery ≥350 minutes (OR 3.17, 1.24-5.20), age ≥6 (OR 3.01, 1.38-6.84) were the independent risk factors for DR in patients with CPB (all P < .05).Extra attention and care are needed for those CPB patients with duration of CPB ≥132 minutes, BUN ≥9 mmol/L, infusion of red blood cell suspension, duration of surgery ≥350 minutes, and age ≥60.

An approach to using pharmacokinetics and electroencephalography for propofol anesthesia for surgery in infants

Safe and effective techniques for propofol total intravenous anesthesia (TIVA) in infants are not well imbedded into clinical practice, resulting in practitioner unfamiliarity and potential for over- and under-dosing. In this education article, we describe our approach to TIVA dosing in infants and toddlers (birth to 36 months) which combines the use of pharmacokinetic models with EEG multi-parameter analysis. Pharmacokinetic models describe propofol and remifentanil effect site concentrations (Ce) over time in different age groups for a given dosing regimen. These models display substantial biological variability between individuals within age groups, impeding their application to clinical practice. Nevertheless, they reveal that younger infants require a higher propofol loading dose, a lower propofol maintenance dose, and a higher remifentanil dose compared with older infants. Proprietary EEG indices (eg, Bispectral Index) can serve as a biomarker of propofol Ce in adults and children to guide dosing to the individual patient; however, they are not recommended for infants as their validity remains uncertain this population. In our experience, EEG waveforms and processed parameters can reflect propofol Ce in infants, reflected by spectral edge frequency (SEF), density spectral array (DSA), and waveform patterns. In our practice, we use a "lookup table" of age-based dosing regimens or target-controlled infusion (TCI) based on the pharmacokinetic models to deliver a target propofol Ce and co-administer remifentanil and/or regional technique for analgesia. We analyze Electroencephalogram (EEG) waveforms, SEF, and DSA to adjust the propofol dose or TCI target concentration to the individual infant. EEG analysis mitigates against biological variability inherent in the pharmacokinetic models and has improved our experience with TIVA for infants.

Electroencephalographic features of discontinuous activity in anesthetized infants and children

Background

Discontinuous electroencephalographic activity in children is thought to reflect brain inactivation. Discontinuity has been observed in states of pathology, where it is predictive of adverse neurological outcome, as well as under general anesthesia. Though in preterm-infants discontinuity reflects normal brain development, less is known regarding its role in term children, particularly in the setting of general anesthesia. Here, we conduct a post-hoc exploratory analysis to investigate the spectral features of discontinuous activity in children under general anesthesia.

Methods

We previously recorded electroencephalography in children less than forty months of age under general anesthesia (n = 65). We characterized the relationship between age, anesthetic depth, and discontinuous activity, and used multitaper spectral methods to compare the power spectra of subjects with (n = 35) and without (n = 30) discontinuous activity. In the subjects with discontinuous activity, we examined the amplitude and power spectra associated with the discontinuities and analyzed how these variables varied with age.

Results

Cumulative time of discontinuity was associated with increased anesthetic depth and younger age. In particular, age-matched children with discontinuity received higher doses of propofol during induction as compared with children without discontinuity. In the tens of seconds preceding the onset of discontinuous activity, there was a decrease in high-frequency power in children four months and older that could be visually observed with spectrograms. During discontinuous activity, there were distinctive patterns of amplitude, spectral edge, and power in canonical frequency bands that varied with age. Notably, there was a decline in spectral edge in the seconds immediately following each discontinuity.

Conclusion

Discontinuous activity in children reflects a state of a younger or more deeply anesthetized brain, and characteristic features of discontinuous activity evolve with age and may reflect neurodevelopment.